After my hugely successful transalp in 2010 I am training for La Marmotte this year and come to the conclusion that I will need a fairly small gear rather than risking having to walk for an hour up hill.

I have a 11 – 25 cassette at the moment combined with a compact crank. I want to go for a 11-32 (I’m not a hero!) but the rear mech (SRAM red) says max 28 teeth.

does anyone know whether that is just because the cage isnt going to be long enough to take slack up in chain that is long enough to go large chainring too large cassette and/or because the mech would catch on the bottom of the cassette and not be able to throw it on and off the cassette? If it is the former I could simply use shorter chain and avoid large to large gear combinations.

any ideas?

ta

woody

You got it with the cage not being long enough to carry the extra lenggth of chain to cover the range needed with a 32t cassette.
A 28t with you compact chain set should give you a pretty low gear. Honestly unless your carrying loads of gear it should be low enough to get you around, especially as your getting some training in.

Put an Apex rear mech on there if you want to run a 32t cassette. Alternatively, do some proper training 🙂

Sounds about right. A normal road mech has a short jockey cage and will take a max 28t. You`ll need a medium cage mech for anything larger. Not sure if Red/Force do 1 or not, you may need to look at rival or the new apex.

basically the mech is designed to work with a specified maximum sprocket size, you can get away sometimes, i used to use a blue 105 with a 13-30 7spd cassette and it worked ok.

What happens is the jockey wheels don’t sit clear of the sprocket. with something like a sram red i would suspect a 30 would be the absolute limit, and i wouldn’t risk a mech costing that much with anything other than what they say, ie 28, they may be better than they were but my experience is SRAM mechs can be delicate.

39t front? 28 will be fine. Off-road 24 x 28 was fine for everyone